[issue46269] '__new__' is never shown in `dir(SomeEnum)`

[Nikita Sobolev]

Change by Nikita Sobolev :


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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue46269] '__new__' is never shown in `dir(SomeEnum)`

[Ethan Furman]

Ethan Furman  added the comment:


New changeset 817a6bc9f7b802511c4d42273a621c556a48870b by Nikita Sobolev in 
branch 'main':
bpo-46269: [Enum] remove special-casing of `__new__` in `EnumType.__dir__` 
(GH-30421)
https://github.com/python/cpython/commit/817a6bc9f7b802511c4d42273a621c556a48870b


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[issue46269] '__new__' is never shown in `dir(SomeEnum)`

[Alex Waygood]

Alex Waygood  added the comment:

Thanks, Nikita! My bad for not adding tests for __new__ in PR 29316.

To confirm: yes, my idea in PR 29316 was that "__new__" (along with most enum 
dunders) should not show up in the output of dir(Enum), but should show up in 
dir(EnumSubclass) if and only if __new__ has been overridden outside of 
enum.py. That's because, unlike with most Python classes, the fact that 
enum.Enum has a __new__ method or a __format__ method doesn't really tell you 
very much about enum.Enum's behaviour, due to how magical enums are. But if 
it's been overridden in a custom Enum subclass, that does tell you that the 
enum class has special behaviour in some way — the HTTPStatus enum at 
Lib/http/__init__.py:6 is a really good example of that.

But you're right: the existing code doesn't work as expected, at all:

```
>>> from http import HTTPStatus
>>> '__new__' in dir(HTTPStatus)
False
```

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[issue46269] '__new__' is never shown in `dir(SomeEnum)`

[Nikita Sobolev]

Change by Nikita Sobolev :


--
keywords: +patch
pull_requests: +28625
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/30421

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[issue46269] '__new__' is never shown in `dir(SomeEnum)`

[Nikita Sobolev]

New submission from Nikita Sobolev :

Right now `__new__` is marked to be special-cased in `Enum.__dir__`.
It is generally ignored:
But, (I think that was the original idea), when `__new__` is overridden, it 
should be added to the output.

But, this line is problematic: 
https://github.com/python/cpython/blame/46e4c257e7c26c813620232135781e6c53fe8d4d/Lib/enum.py#L656

Why? Because `self.__new__` is always `EnumMeta.__new__`. Original `__new__` is 
renamed to `_new_member_`.

This behavior is also not tested.

So, my proposal is: let's always remove this method from `__dir__`. Why?
- If we modify the check above to compare `_new_member_`, we will show 
`__new__` as the output. It is kinda misleading
- `__new__` is not supposed to be overloaded in `EnumMeta`, it is very special
- `__new__` is a very basic thing. It would be kinda strange not to see it for 
some cases, but to see it for others. For example, all (?) other data types 
always show `__new__`, even if it is not explicitly defined:

```
>>> class A:
...def __new__(*args, **kwargs): ...
... 
>>> assert '__new__' in dir(A)

>>> class B: ...
... 
>>> assert '__new__' in dir(B)
```

I guess being consistent here (we don't show `__new__` at all times) is better.

I will send a PR that removes these two lines in a moment! Any other ideas are 
much appreciated! 

Related:
- https://bugs.python.org/issue45535
- https://github.com/python/cpython/pull/29316

--
components: Library (Lib)
messages: 409771
nosy: AlexWaygood, ethan.furman, sobolevn
priority: normal
severity: normal
status: open
title: '__new__' is never shown in `dir(SomeEnum)`
type: behavior

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